The new "My Ref" Rev C thread

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Bill_P

Bill_P

Member
Joined 2009
udailey said:
There is no danger. The resistor is a tiny part of the load, especially with 8Ohm speakers. Imagine that you put max 35W into your speakers.. how much would actually dissipate in the resistor?
Click to expand...

At 35W into 8 Ohms the resistor dissipates 2.2 Watts. With no heatsink Caddock rates the resistor at 1.25 Watts at which point the resistor reaches 150C in a 25C ambient.

So the resistor will not survive extended full power testing at 35 Watts output into 8 Ohms. In practice the average music power into 8 Ohms is not 35 Watts and should be considerably less. With fairly efficient speakers and moderately loud volume, the resistor should be within its ratings. If you like your music very loud and/or have inefficient speakers, better use a heatsink on the resistor.
 
ClaveFremen

ClaveFremen

Member
Joined 2005
inserra.it
Paid Member
Bill_P said:
If you like your music very loud and/or have inefficient speakers, better use a heatsink on the resistor.
Click to expand...

Like this one? ;)
 

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L

lloop9

Member
Joined 2004
Guys, has anyone implemented Bill P's recommended mods of improving the circuit via:

- replacing R14 with a LM7824 regulator & an additional filtering cap for better voltage regulation to the relay?

- clamping diodes across polarized C15 & C16 to limit negative voltage?

Any feedback on these mods?
 
B

bcmbob

Member
Joined 2009

Hi All, I finally got the Mundorf M-Lytic AG caps installed in the V1.3 amps. It's only been a few hours but there is a noticeable change/improvement. It shows mostly in the lower mids and especially the bottom end. The overall sound seems "mellower" where it should be without taking away any of the crispness, dynamics and punch.

The most noticeable improvement is in the definition and stability on the low end. At first I thought I was hearing less bass and in some sense I am. After a few different flavors of music, I get the impression the new caps reduced a slight element of "boominess" that I had noticed on heavy bass tracks with the speakers I'm using. One often used description of Vifa tweeters is that they are very fast. I would apply that phrase to the effect these caps have on the low end. The notes start and stop with more accuracy and less carry over.

I have not done the pipe organ stuff yet but the synth and acoustic basses and kick drums still have the propper weight but again come through with an element of tighter definition. I'm going to try to do an A-B comparison with the V1.2 amps (with the old caps installed) but will wait till I get some pin sockets as I soldered both ends of the wires between the MyRefs and the Lighter Note.

This mod is nowhere as dramatic as the Sonicaps and Black Gates, (I don't think anything is) but are well worth the cost ($25 ea.) to those builders trying to squeeze all they can from the MyRefs.

I have some new Neotech hook-up wire on hand now, but won't place it till I get everything in the new chassis I'm building.

More to come........

P.S. Shucks - the first snow of the season just started. Anybody got a cabin in Bimini I can use for a few months ?:cool:
 
B

bcmbob

Member
Joined 2009
AC Fuses

I forgot to mention I had a couple AC fuses blow at power-up (after using the dim bulb) during my latest rework.All is fine now but I don't recall any conversations on this subject. I have been using 120VAC with two ApexJr 24-24 transformers plus the Lighter Note 12-12 for months without any problems. My final build will have two Antek 22-22 plus an 18-18 for a preamp/buffer I want to add. Any suggestions or formulas for proper fuse ratings for such a setup?
 
M

mx2

Member
Joined 2007
Hi guys...I need help!

I just finished soldering up my MyRef and hooked it up for testing. When I turned it on, I heard a pop and saw sparks. It seems like I blew DR1 and DR2. Any theories for what happened? Can it be saved? :(

My other channel worked fine, but I didn't hook up the heatsink this time. Do you think the heatsink could have caused DR1 and DR2 to blow on the first channel?

Thanks!!
 
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